It has become quite commonplace to use pipes and conduits made of plastics for carrying highly corrosive liquids which may be extremely caustic or acid in nature. The plastics employed have varied considerably in nature but are oftentimes of a fluorcarbon resin plastic which is highly resistive to corrosive liquids. Fittings for such pipes and conduits have been made of plastic and have been improved so that extremely tight seals are obtained between the fittings and the lengths of tubing or conduit. Typical of such fittings are those illustrated in U.S. Pat. No. 3,977,708.
Suitable valves for use in conveying systems for highly corrosive liquids have not been commonplace. Considerable difficulty has been experienced in the use of ordinary valves because of the extremely sensitive nature of such valves to highly corrosive liquids.